OTTAWA — Treasury Board President Scott Brison, one of the most experienced hands in the government of Prime Minister Justin Trudeau, is quitting politics — but a court case centred on Vice Admiral Mark Norman is sure to keep him in the public spotlight.

Brison said the Norman trial, scheduled to begin in August, had no bearing on his decision to leave politics. “If that issue had never occurred, I would be making the same decision that I’m making now,” he told the Canadian Press.

But Brison will face withering examination from defence lawyers for Norman, who have focused on Brison’s role in pausing a $700-million navy supply ship procurement. Norman is facing a criminal charge of breach of trust for allegedly leaking cabinet secrets about the project. The Crown’s witness list, disclosed in court last month, includes Brison.

Evidence filed in court shows Brison had urged his colleagues to pause the project with Davie Shipbuilding until more study was done. At a crucial Nov. 19, 2015, cabinet committee meeting, Brison introduced a letter from Davie’s rival Irving Shipbuilding that called on the government to consider its own proposal. News of the meeting immediately leaked, and Brison vented fury over the leaks during a later interview with the RCMP, portions of which were filed in court.

Scott Brison speaks during question period in the House of Commons on Oct. 16, 2018.Adrian Wyld/The Canadian Press

Brison has since said he was simply trying to do due diligence on a sole-sourced project signed in the final days of Stephen Harper’s Conservative government, and has strongly denied allegations by Norman’s lawyers that he was unduly influenced by Irving.

Brison’s departure marks the end of a 22-year career on Parliament Hill that has seen him known as a rising Progressive Conservative star, a floor-crosser to the Liberals, a foiled leadership candidate for two parties and Canada’s first openly gay cabinet minister.

The Nova Scotia MP said Thursday he’s resigning from cabinet and won’t run for re-election in 2019. In a statement, he cited three reasons for stepping down: to leave while he was at the height of his career, to pursue new opportunities while he still can, and to spend more time with his husband and twin four-year-old daughters.

“I’m proud of what I helped accomplish,” he said in the statement. “I’m leaving on top, proud of my Prime Minister and our government.”

From the day Brison was first elected in 1997, he was seen as a young political star and a potential party leader.

He was elected into the shrinking caucus of the Progressive Conservatives, which was rapidly losing support on its right flank. At 31 years old, Brison was seen as the possible future of the PCs. But in the leadership race he threw his support behind Joe Clark, and even temporarily gave up his seat in 2000 to allow Clark to sit in the House of Commons.

When Clark stepped down two years later, Brison entered the race to replace him but lost to fellow Atlantic MP Peter MacKay. Within months MacKay negotiated the merger of the PCs with the Canadian Alliance, creating today’s Conservative Party.

In the final weeks of the unite-the-right negotiations, Brison was already publicly expressing skepticism. He had come out as gay the year before and was concerned about giving too much power to social conservatives in the Canadian Alliance.

The merger was made official on Dec. 8, 2003. Two days later, Brison announced he was defecting to the Liberal government under Prime Minister Paul Martin.

Candidate Scott Brison, left, throws his support behind Jim Prentice after being defeated in the second ballot at the federal PC leadership convention in Toronto on May 31, 2003.National Post file

In his role as an opposition finance critic, Brison had badgered Martin relentlessly. Just a year earlier, he’d attacked Martin as “timid” and “risk averse.” But Brison held onto his seat in the 2004 election, which delivered a Liberal minority government, and Martin appointed him to cabinet as minister of public works.

Brison was the first openly gay cabinet minister in Canadian history, a big milestone for a country in the midst of a momentous gay rights debate. A year later, same-sex marriage was legalized; Brison married his partner Maxime St-Pierre in 2007.

“The House of Commons didn’t just shape my career – decisions made in that room shaped my life,” Brison said in his statement on Thursday. “Including decisions that gave me the opportunity to marry the person I love, and raise a family while being open and honest about who I am as a person.”

The Liberals lost the election in January 2006, perhaps in part due to the mid-campaign revelation that the RCMP was investigating a possible leak of cabinet information on taxing income trusts. Brison was soon deep in the scandal after it emerged he’d sent an email to a friend at CIBC that appeared to be a tip-off about the income trust decision.

Brison defended himself by saying he was only discussing rumours that were in the public realm. He was never charged with any offence. But the defence team for Norman has not missed the irony of this, pointing specifically to the income-trust scandal as evidence that leaks in Ottawa are common — and rarely prosecuted as a criminal matter.

Martin stepped down after the election, and for the second time Brison entered a leadership race. But he finished near the back of the pack, and spent the next decade as a prominent critic on the opposition benches.

The 2015 election that saw the Liberals return to power also saw Brison return as a cabinet minister. But in contrast to the Martin era, Brison has been a low-key minister in the Trudeau government. Aside from the Norman trial, he has mostly been in the spotlight over the government’s much-criticized reforms to the access-to-information regime.

On Thursday, Trudeau thanked Brison for his “extraordinary service”, calling him someone who “every day dedicated himself to his country, to his community and to building a better future for all.”

Asked whether the Norman trial played any role in the resignation, Trudeau said he’d “accepted Scott Brison’s decision based on his desire to spend more time with family, and that is certainly something that I can understand as a father of young kids myself.”